Manoeuvring arrangement of steam turbine



Nov. 8, 1960 TSUNEO ANDO ETAL MANOEUVRING ARRANGEMENT OF STEAM TURBINEFiled May 24, 1955 4 Sheets-Sheet i INVENTOR. Tsuned Ando lppei Ir ieMaxwell E.Spurrow ATTORNEY.

Nov. 8, 1960 TSUNEO ANDO ETAL 2,959,182

MANOEUVRING ARRANGEMENT OF STEAM TURBINE 4 Sheets-Sheet 2 Filed May 24,1955 INVENTOR. Tsuned Ando lppei lrle Maxwell E. Sparrow II 1! 7/22? AATTORNEY.

NOV. 1960 TSUNEO ANDO ETAL 2,959,182

MANOEUVRING ARRANGEMENT OF STEAM TURBINE Filed May 24, 1955 4Sheets-Sheet 3 57 o 5 55 40 I P3 52 53 P6 FIG .3

INVENTOR. ed Ando BY 1 Irie Maxwell E. Sparrow ATTORNEY.

Nov. 8, 1960 TSUNEO ANDO ETAL 2,959,132

MANOEUVRING ARRANGEMENT OF STEAM TURBINE Filed May 24, 1955 4Sheets-Sheet 4 INVENTOR. Tsuned Ando lppei ir'ie Maxwell E.SporrowATTORNEY United States Patent MANOEUVRING ARRANGEMENT OF STEAM TURBINETsuneo Ando and Ippei Irie, Kobe, Japan, assignors t0 Kawasaki JukogyoKabushiki Kaisha (Kawasaki Dockyard Co., Ltd.)

Filed May 24, 1955, Ser. No. 510,728

7 Claims. (Cl. 13718) This invention relates to manoeuvring devices ofsteam turbines, preferably of ships turbines, in general and tohydraulic devices of this kind of machine in time it is important tomaintain the necessary pressure of the main bearing lubricant to keepthe prime mover from becoming inoperable during the time when alloperations of the vessel depend upon its proper function. In addition tothis condition, a manoeuvrable condition of the ship has to bemaintained all the time during storm periods when there is the danger ofoverspeeding of the steam turbine due to propeller racing.

Devices and apparatus have been designed to meet the various conditionsoutlined above, but either they are independent from one another or theyare complicated mechanisms which require special skill to handle.

Objects and advantages of this invention will be set forth in parthereafter and in part will be obvious herefrom or may be learned bypracticing the invention, the same being realized and attained by meansof the instrumental'ities and combinations pointed out in the appendedclaims.

The invention consists in the novel parts, construction, arrangements,combinations and improvements herein shown and described.

It is the principal object of this invention to provide for new andimproved means of manoeuvring controls for ships turbines.

It is a further object of this invention to provide for a device whichby virtue of its servo action can be operated lightly, easily and fast.

Another object of the invention is to provide for a controlling means bywhich the adjustment of the flow of steam or a like motive fluid can beregulated promptly and easily at all times in equal increments ofturning angle of the control hand wheel regardless of the posi: tion ofthe main steam valves.

A further object of the invention is to provide for a hydraulic meansfor controlling and manoeuving a steam turbine which utilizes a part ofthe lubricating oil of the turbine unit as its pressure fluid and whichis included in the system of the lubricant lines.

This includes another object of the invention, that is, to provide for afoolproof device in the sense that the operator cannot set the controlsin motion after the mechanism has shut down in an act of emergency, unless the whole system of pressure balance in the pipe lines is restoredto the normal state.

Another object, connected directly with the foregoing, of this inventionis to provide for means to return the complete mechanism of the pipelines automatically to its original position after the dangeroussituation causing the emergency action is over, and to restoreautomatically the functions ascribed to the mechanism without otherextraneous hand operation.

I A further object of the invention is to provide for a controllingdevice by which the steam flow to the turbine automatically is shut offin case of a pressure failure of the lubricant oil whereassimultaneously an emergency flow of lubricant oil to the main bearingsof the turbine unitis maintained through a special safety valve and froma separate supply tank until the turbine shaft eventually ceases torotate.

Another object of the invention is to provide for a controlling meanscomprising a stationary head tank which by virtue of its arrangementwithin the control system is kept full of oil.

A further object of the invention is to provide for a mechanism whichoperates by the pressure differential between two oil lines causingautomatically the stopping of the turbine unit in case of overspeeding.

Another object in connection with the aforementioned one is to providefor control means which can be adjusted with respect to the overspeedlimits and which permits testing the whole system at a safe lower speedof the turbine unit without altering the relationship between thevarious cooperating elements of the control device.

Furthermore, it is an object of this invention to provide for adjustableautomatic control means for conditions of navigating with light draft orin storm conditions keeping the usual economic speed without abandoningthe safety of operation.

Various further and more specific objects, purposes, features andadvantages will clearly appear from the detailed description given belowtaken in connection with the accompanying drawings which form a part ofthis specification and illustrate merely by way of an exampleoneembodiment of the device of the invention.

The invention consists in such novel features, arrangements andcombinations of parts as may be shown and described in connection withthe apparatus herein disclosed by way of an example only and asillustrative of a preferred embodiment.

In the following description and in the appended claims, parts will beidentified by specific names for convenience, but such names areintended to be as generic in their application to similar parts as theart Will pe mit. Like reference characters denote like parts in theseveral figures of the drawings, in which: 4

Fig. 1 shows a pipe line diagram and the complete arrangement of thedevice;

Fig. 2 is a cross section of the main ahead and astern manoeuving steamvalve A and of the servo oil cylinder B, as shown in Fig. 1; v

Fig. 3 is a cross section of the servo oil cylinder B and the pilotvalve C attached thereto, taken along theline 3-3 of Fig. 4; I

Fig. 4 is a horizontal section of the servo oil cylinder B shown in Fig.3, taken along the line 4-4, partly broken away; I

Fig. 5 is a vertical section of the servo oil cylinder 13 shown in Fig.4, taken along the line 55;

Fig. 6 is a cross section of the pressure sensing valve PV with thesafety valve SV attached thereto, as shown in Fig. 1;

Fig. 7 is a cross section of the emergency valve EV, shown in Fig. 1. U

Referring now in more detail to the drawings illustrate ing a preferredembodiment by which the invention may be realized, there is a main valveassembly for mae noeuvring a head and .astern, generally designatedbythe letter A, connected directly to a servo oil cylinder B to which apilot valve C is attached. A manoeuvring stand h having the conventionalhandwheel and connecting shafts and two emergency control wheels h and hare connected to the valve assembly A, B and C. The steam turbine T hastwo oil pumps of the impeller type ll; .114

ends.

IP, for ahead and astern rotation attached to its main shaft which arepumping oil under pressure through the pipe line P into the pilot valveC. Pressure in this pipe line may be adjusted by an adjusting valve AV.Pressure adjusting valves RV in the two discharge lines of 'the impellerpumps 1P and 1P provide for means to balance the oil pressure for aheadand astern drive. The

two impeller pumps 1P and 1P receive the oil from the main oil supplypump P which draws the oil from the main reservoir DT into which alldischarge lines lead. Said main supply pump P also feeds oil underpressure into a high tank HT through pipe line P and through a coolingdevice CL and a filter F. The oil coming down from the high tank HTflows to the main bearings of the turbine at the entering point 1 andsubsequently is drained back to the reservoir DT.

A third branch line P feeds oil under pressure from the main oil pump Pinto a safety valve SV and into a pressure sensing valve PV through pipeline P Two pipe lines emerge from the pressure sensing valve PV:Pcontinuing into the intake port of the servo oil cylinder B, and Pleading to the intake orifice 62 of the pilot valve C. The outletopening of the safety valve SV is connected by a big pipe line P to themain bearing oil feed line coming from the high tank HT and thus isfeeding back oil pressure from this tank to the valve SV. A branch lineleads from the pressure line P to an emergency valve EV the discharge ofwhich is drained directly into the reservoir DT.

The main manoeurvring valve A comprises a valve body 11 having a mainsteam intake opening 12. The steam or the motion fluid or the like canflow either through the ahead valve 13 or through the astern valve 13'and from there through the corresponding outlets 14 and 14' to thecorresponding ahead or astern turbines. Valve stems 15 and 15 of'thevalves 13 and 13' project to the outside of the valve body 11 havingrespectively spring supports 16 and 16' attached to their lower Coilsprings 17 and 17' placed between the valve body 11 and the springsupports 16 and 16 are pressing the valves 13 and 13' constantlydownward and thus provide for the tendency to have said valves shut.Connecting links 18 and 18 join said valve stems 15 and 15 with the twoends of a lever 19 which is pivotally supported in its center by a shortstud 20 held by a bracket 21 which bracket is attached to the upper partof the servo oil cylinder generally designated in the figures by theletter B. On the side of the ahead valve stem 15, an extension 23 of theoil piston 24 is connected with the pivotal point 22 of the lever 19.

Said oil piston 24 of the servo oil cylinder B has a vertical bore 25 inits center and has a peripheral groove 26 in the equatorial place of itsbody, forming a space between cylinder wall and piston which space isconnected by a horizontal bore 27 to a circular space 42 around thevertical bore 25 and which is connected to the pipe line P Above andbelow said circular space 42 there are two grooves 28 and 28 arrangedconcentrically to said vertical bore 25. These concentric grooves 28 and28' are connected by two corresponding channels 29 and 29' to the upperand lower side respectively of the piston 24. A hollow pilot sleeve 30is fitted in the vertical bore 25 of the piston 24. This pilot sleeve 30projects downward through the bottom of the servo oil cylinder B and hasa forked end 31. Pins, not shown in the drawing, are arranged in the twoprotruding ends of said fork 31 and engage right and left incorresponding grooves of a cam 33 (grooves not visible in the drawing),which cam is firmly attached to the shaft h of the manoeuvringhandwheel.

The pilot sleeve carries ring-shaped cylindrical faces 34 and 35arranged in such way that they may just close the circular grooves 28and 28 in their middle position. Bores 37 and 38 in the well of thepilot sleeve connect the inner bore 36 of said pilot sleeve to thesurrounding area between said pilot sleeve and the inner wall of thevertical bore 25. A further series of bores 39 connects the inner bore36 of the pilot sleeve to a circular discharge chamber 40 having anoutlet 41 and a pipe line P leading to the oil reservoir DT (Fig. 1).

Attached to the servo oil cylinder B is a pilot valve, generallydesignated by the letter C, which has two parallel vertical passageways51 and 52 in its body 50 which passageways are connected, respectively,by channels 54 and 55 to the upper and to the lower side of the oilpiston 24. A piston valve 57 operating in the vertical bore 52 has apressure plate 58 on top of which is arranged a compression spring 60the force of which can be adjusted by a screw 59. Oil pressure lines Pand P are connected to the intake openings 61 and 62 of the pilot valveC.

As mentioned above, the oil pressure lines P and P which lead to theintake openings of the servo oil cylinder B and to the opening 62 of thepilot valve C are coming from the pressure sensing valve PV to which thesafety valve SV is attached. As shown in Figure 6, the pressure sensingvalve is a double valve comprising the two valve bodies 70 and 70containing an upper valve 71 for the pipe line P and a lower valve 72for the pipe line P therein. The two valves are connected by a commonvalve stem 73 and have on top of it a compression spring 74 the force ofwhich is adjustable by a screw 75.

The safety valve SV is a regular safety valve comprising a valve and aspring 81 in a housing 82. The connection of it to the pressure sensingvalve PV is made in such a way that oil under pressure in the pipe lineP may open the safety valve against the combined spring force of thespring 81 and the static head pressure of the high tank HT in order todischarge directly through the big pipe line P into the main bearings ofthe steam turbine.

The emergency valve EV, as illustrated in Fig. 7, comprises in a valvebody 96 a valve 91 operating against a valve seat forming part of avalve stem 92 which extends upwardly and which is forced down by aspring 93 thus having the tendency to stay open. Said valve stem has onits upper end a collar 95 having a protruding flange 94. The collar 95is connected to a handwheel 97 by means of a spline 95 which handwheelcan be turned freely on top of the housing 96 but cannot be moved up anddown by virtue of a ring 97'. Thus the collar 95 can be turned by thehandwheel 97 and can slide up and down in it. Hooks 98 pivotally mountedon the valve housing 96 having handles 99 are supporting the collar 95by means of the protruding flange 94 and thu are keeping the valve 91 ina certain preset position against the spring pressure.

In order to control the turbine manoeuvers by hand in a case ofemergency due to failure of the automatic system, there are arranged ontop of the main valve body (Fig. 2) levers 100 and 101 which have on oneend a small piston rod 102 and 102 and pistons 103 (corresponding part103' not shown) and connecting shafts and gears and handwheels h and hby which the valves 13 and 13' may be operated if the oil pressure isnot strong enough to move the valve stems 15 and 15.

Operation The description of the operation may start with the assumptionthat a normal state of running of the steam turbine has been reached. Asit is shown in Fig. l, the flow of the lubricant oil of the mainbearings of the turbine shaft follows a closed circuit into which thevarious control elements are built. Oil under pressure is supplied bythe main lubricant oil pump P, the high tank HT is filled through pipeline P and oil flows into the bearings, and circulates back intoreservoir DT. Through the connecting line P oil pressure is brought ontop of the safety valve SV where the valve 30 is kept closed by said oilpressure and the additional spring pressure of the spring 81. At thesame time, oil is fed through the branch lines P and P into the pressuresensing valve PV and under the valve 80 of the safety valve SV, andsince a balanced state against the spring 74 is reached, oil flows intothe servo cylinder B and into the line 62 of the pilot valve C. A partof the oil may bleed through the emergency valve back into the reservoirDT for reasons which will be described later, thus lowering the pressurein the line P Since the turbine is running, the impeller pump IP (or 1Pfor the opposite direction'of rotation) which is directly driven by theturbine shaft, supplies oil which it receives from the main pump P,under a pressure corresponding to its speed, through pipe line P intowhich regulating valves and an adjusting valve AVare inserted, into theupper part of the pilot valve C through the orifice 61. Thus, a state ofbalance between oil pressure from the impeller pump IP; with the springpressure of the spring 60 on one side and the oil pressure from oil lineP on the other side has been established, the piston .24 is in a liftedposition according to the position of the pilot sleeve 30, which in turnis determined by the position of the control wheel h and the cam 33, andthe ahead steam valve 13 is open accordingly, admitting the right amountof steam to the turbine. Any change in the position of the controllingwheel h changes by virtue of the profile of the cam 33 the position ofsaid pilot sleeve 30, whereby the grooves 28 and 28 are opened, oilunder pressure supplied by pipe line P can enter the area below or abovethe piston 24 through the passages 29 or 29' and raises or lowers saidpiston and the main steam valve 13 (or 13) exactly as much as theposition of said pilot valve 30 indicates; that is, until the grooves 28and 28' are closed again by the rising piston. When the lever 19 is in ahorizontal position, both main steam valves 13 and 13' are closed, thecontrol wheel shows the neutral position and the piston 24 of the servooil cylinder B is in its center position, as shown in Fig. 3. Any turnof the control wheel h in one or the other direc tion will raise orlower immediately by the oil pressure and piston and will open or closeby the valve stems 18 or 18' the ahead or astern steam valves wherebythe connection of the valve stems 18 and 18 with the lever 19 is made insuch way that the springs 17 and 17' can .keep one valve shut while theother is lifted. It is obvious to those skilled in the art that by aproper profile of the cam 33 the increase and the decrease of the steamflow can be controlled in a linear proportion to the turning angle ofthe control wheel h and that the operation is attained with great easeand precision due to the servo action of the piston 24.

So far the pressure differential between the oil in the line P comingfrom the impeller pumps 1P or IP in.- creased by the adjustable springpressure of the spring 60 on one side and pressure in the line P comingfrom the pressure feeler valve on the other side, has been considered asbeing in balance. Therefore, the cylinder valve 57 kept the opening 55closed. If by any one of the reasons given below the pressuredifferential is no longer maintained, that is, if either the pressure ontop of the valve 57 increases or if the counter pressure in the line Pdecreases, said valve 57 opens the connecting lines between the upperand the lower area of the piston 24, thus equalizing the pressure in thetwo areas and causing the springs 17 or 17 to close automatically themain steam valve. When the cause of the unbalance again is removed, thevalve 57 automatically returns to its original position. Consequentlythe piston 24 returns by the oil pressure coming from pipe line Pautomatically to the position indicated by the pilot sleeve 30, thusopening the steam valve 13 or 13' whereupon the turbine resumes itsnormal running.

The reasons for an unbalance of the oil pressure differential in thepilot valve C and thus for a change of the position of the valve 57 canbe the following:

(I) The oil pressure in the pipe line P can increase by d an increase ofthe pressure from the impeller pump 1P (or 1P due to over-speeding ofthe turbine that happens for example when in a storm the ships propellergets out of the water and starts racing. (2) The pressure below thevalve plate 58 and the valve 57 can decrease, if:

(a) The oil pressure of the main lubricant oil pump P drops; (b) Thesafety valve SV opens; (c) The oil pressure in the pipe line P drops dueto opening of the emergency valve EV.

The oil pressure of the main lubricant oil pump can drop for thefollowing reason.

As shown in Fig. 1, the pressure sensing valve PV, described in Fig. 6,is built into the pipe lines P and P at the point where these linespart, in such a way that both pipe lines may be shut by the valve. As itis shown the adjustable spring 74 tends to keep the valve closed. Oil issupplied constantly by the main lubricant oil pump P through theparallel line P through the filter F and the cooling device CL into thehigh tank HT, thus supplying the necessary oil to the turbine shaftbearings. If the pressure of the pump is high enough to keep the levelof oil in the high tank HT, the oil pressure is suflicient to open thedouble valve 71 and 72 against the spring pressure. Thus, oil issupplied under pressure to both the pilot valve C and to the servo oilcylinder B; In case the main lubricant oil pump would stop or in caseits pressure would not be more sufiicient to feed oil'into the high tankHT, the force of the spring 74 would be greater than the oil pressureand the valve 71 and 72 would close. This in turn lowers the pressureunder the pilot valve C, and, as described before, would shut off thesteam supply to the turbine. In other words, it is the differentialbetween the dynamic pressure from the pump P and the static pressurefromthe high tank HT which controls the position of the pressure sensingvalve PV against the force of the adjustable spring 74 by the action ofthis pressure differential on the safety valve SV, as explained above.

Directly connected with the pressure feeler valve PV is the safety valveSV, as shown in Fig. 1 and Fig. 6. This valve is kept closed by the oilpressure in the big connecting line P which is the same static pressureof the high tank HT as mentioned before, increased by the force of thespring 81 on top of the valve'80. Through the connecting pipe line P thedynamic pressure ofthe main lubricant oil pump P is acting against thestatic oil pressure and the spring pressure. Under normal operatingconditions, if the high tank HT is full, the additional force of thespring 81 is set in such a way that the combined static and spring forceis greater than the dynamic force of the pumps and keeps the valveclosed. But when the oil level in the high tank drops, the combinedstatic and spring force can not keep the valve closed any longer againstthe dynamic force of the pump P. Consequently, the valve opens and oilis supplied directly to the turbine shaft bearings through the big pipeline P At the same time, the dynamic pressure from the pump P drops inthe pipe lines P and P the pressure of the spring 74 closes the doublevalve 71 and 72 and again the pilot valve C and the servo oil cylinder Bcloses automatically the steam fiow to the turbine.

This arrangement also prevents the turbine to be set in motion until thehigh tank HT is filled with oil and until the oil pressure supplied bythe main lubricant oil pump has reached a sufficient level.

It also provides for suflicient emergency lubrication during the timewhen the turbine unit runs by the inertia of the rotor after the steamsupply is shut off, because the shaft bearings receive the lubricant oildirectly through the pipe line P and the danger of damage is avoided.

If in turn some trouble should occur in the pump P itself, the doublevalve 71 and 72 closes before the dy 7 namic pressure from the pump Pbecomes weaker than the static pressure of the oil in the completelyfilled high 'tank HT. Therefore, sufficient oil is available from thehigh tank HT at the time when the rotor of the turbine "starts to run byits'inertia only until it eventually stops.

If the pump P still continues operating, although at a lower rate, afterthe pressure sensing valve PV has closed, the safety valve SV whichclosed when the dynamic pressure from the pump P dropped, opens again,when the static pressure of the high tank HT, sinking as the oil in itis more and more used up, reaches a level lower than the rate. at whichthe pump is operating, and as much lubricant oil as possible is suppliedto the bearings of the turbine rotor.

The oil pressure in the pipe line P can be lowered by the operation ofthe emergency valve EV, as shown in Fig. l and described in more detailin Fig. 7. This operation serves three purposes.

First, under normal conditions and circumstances, a part of the oilunder pressure in the pipe line P is permitted to drain back into thereservoir DT by setting the position of the valve by means of thehandwheel 97. Thus, the pressure in the pipe line P can easily becontrolled and adjusted.

Second, in a case of emergency, if the turbine unit has to be stopped atonce, moving the handle 99 downward releases the hooks 98, the spring 93opens the valve immediately and completely whereupon all the oil in thepipe line P flows into the reservoir DT. The pilot valve C opensimmediately and the servo oil cylinder B shuts the main steam valves ofthe turbine.

Third, if the pressure sensing valve PV reacts on trouble in thecirculation system of the lubricant oil and cuts the flow of oil to thepipe lines P and P off, the pressure in the pipe line P drops due to thecontinuous drain of oil through the emergency valve. This again causesthe pilot valve C to open and consequently to shut olf the main steamvalves.

There is an additional advantage provided for by the emergency valve EV.The operator is enabled to adjust the amount of oil which is draineddirectly back to the reservoir DT and by this adjustment he can changeat his will the limit of overspeed of the turbine at which limit thesteam valves are automatically closed.

The oil pressure in the pipe line P depends directly upon the adjustmentof the emergency valve. The pressure of the oil in the pipe line P whichis acting on the valve plate 58 for opening the valve 57, depends uponthe speed of the impeller pump 1P (or 1P said speed being proportionalto the speed of the turbine. By said adjustment it is possible toarrange that the oil pressure in the pipe line P builds up rapidly at alower speed to the pressure level in the pipe line P Thus, the pilotvalve C operates at a speed of the turbine which is lower than thenormal speed.

The usefulness of this device may be explained. It cannot be avoidedthat a ship having a common steam turbine slows down her speed in astorm during her navigation with light draft. This means to keep thespeed of the turbine unit far below its regular horsepower as itfrequently falls into a state of danger when the speed of the turbineunit reaches the overspeed limit due to propeller racing. With a deviceas described herein a ship can continue her navigation as a fixedeconomical speed with the overspeed limit of the turbine only set closerto the normal speed by merely adjusting the amount of oil drain throughthe emergency valve. The turbine unit stops at all time with theautomatic action of the pilot valve when the preset overspeed limit dueto propeller racing is reached, but resumes it original function, whenit falls below the regulated speed because the pilot valve C returns toits closed position, the servo oil cylinder piston returns to itsposition coinciding with that of the pilot sleeve 30 which is set by thehandle 21 and so the navigation keeps on going automatically.

Furthermore, at the routine performance test of the manoeuvring valvesit is possible to test all functions at a lower overspeed limit than itsregular speed, and it is not necessary to run the turbine up to its topspeed.

While the invention has been described and illustrated with respect to acertain particular preferred example which gives satisfactory results,it will be understood by those skilled in the art after understandingthe principle of the invention, that various other changes andmodifications may be made without departing from the spirit and scope ofthe invention and it is intended therefore in the appended claims tocover all such changes and modifications.

We claim:

1. A reversible prime mover having bearings and ha ing spring-loadedahead and astern admission valves having a manoeuvring device, andcomprising a doublearm lever, said valves having stems and havingsprings mounted on said stems means at the ends of the arms of saiddouble-arm lever for supporting the stems of said admission valves, ahydraulically operated servomotor having orifices for connections topipe lines having a piston therein connected by a linkage with saiddoublearm lever acting against the springs of the ahead and asternadmission valves and having passages therein connecting its hollowcenter portion with the upper and the lower side of said piston, ahollow pilot sleeve in the hollow center of said piston having a stemextending through said piston and having a cam-shaped operating memberat the end of said stem, a pilot valve attached to said servo-motorhaving passages connected to the upper and the lower side of said pistonof said servo-motor, manually operable means to actuate said hollowpilot sleeve by said cam-shaped member, a main pumping means forlubricant oil for the bearings of said reversible prime mover, impellerpumps for said lubricant oil driven by the ahead and astern parts ofsaid prime mover, respectively, and pipe-lines connecting said mainlubricant oil pumping means and said prime mover driven impeller pumpswith corresponding orifices of said servo-motor and said pilot valve,respectively, said pilot valve having pistons; said piston of saidservo-motor being actuated by the pressure of the lubricant oil comingfrom said main oil pumping means which action is controlled by themanually operated cam and the said hollow pilot sleeve, and beingactuated also by the differential between the oil pressure of said mainoil pump and the oil pressure of said prime mover-driven impeller pumpsacting upon the lower and the upper face of the said pistons of saidpilot valve attached to said servo-motor, respectively when suchpressure differential exceeds a predetermined amount.

2. A reversible prime mover having bearings and having spring-loadedahead and astern admission valves having a manoeuvring device, accordingto claim 1, and wherein said cam-shaped operating member has a profilefor controlling the increase or decrease of the flow of the drivingfluid for the prime mover in' a proportion linear to the positioning ofthe manually operated control means.

3. A reversible prime mover having bearings and ahead and asternadmission valves connected with a double armed lever, said valves havingstems and having springs mounted on said stems, means at the ends ofthe'arms of said double armed lever for supporting the stems of saidadmission valves, a hydraulically operated servomotor having a pistontherein connected by a linkage with said double armed lever actingagainst the spring of the ahead and astern admission valves, a pilotvalve attached to the servo-motor, said pilot valve having an intakeport connected to a source of constant pressure and an intake portconnected to a source of variable pressure, said pilot valve havingmeans therein operable by a drop of said variable pressure to connectsaid pressures to opposite sides of said piston to thereby close saidadmission valves, a main pumping means for lubricant oil for thebearings of said reversible prime mover, said main pumping means alsoproviding the source of said Variable pressure, a high storage tank forsaid lubricant oil connected by pipe lines with said main oil pumpingmeans, a spring biased closed pressure sensing valve connected by a mainpipe line between said main oil pumping means and said pilot valve, andby an auxiliary pipe line between said main oil pumping means and saidservomotor piston, said pressure sensing valve being held open bypressure in the main pipe line, a safety valve connected between saidmain pumping means and said pressure sensing valve, said safety valveopening upon a drop in the level of the oil in said high storage tankfor allowing oil to pass from said main pipe line to said bearings.

4. The structure as set forth in claim 3, said high storage tankconnected to said safety valve and providing fluid pressure on one sideof the safety valve tending to hold it closed, said safety valve havinga spring biasing the safety valve closed, the fluid pressure in the mainpipe line tending to open the safety valve.

5. The structure as set forth in claim 3, an emergency valve connectedbetween the pressure sensing valve and 10 the pilot valve allowing aslight flow of fluid out of the main pipe line, said emergency valvehaving a manually operative trip to open the valve completely.

6. The structure as set forth in claim 3, including manually operatedmeans for controlling the flow of fluid from the main oil pumping meansthrough the auxiliary pipe line to the servo-motor piston for operatingsaid spring loaded admission valves.

7. The structure as set forth in claim 3, said source of constantpressure comprising impeller pumps for connection to said prime mover,said impeller pumps being connected in a pipe line between said main oilpumping means and said pilot valve.

7 References Cited in the file of this patent UNITED STATES PATENTS1,859,437 Flanders May 24, 1932 1,902,311 Reavis Mar. 21, 1933 2,197,743Crafts et al Apr. 16, 1940 2,440,844 Bryant May 4, 1948 FOREIGN PATENTS762,155 Great Britain Nov. 21, 1956

